• Structural Engineering and Mechanics
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• v.52 no.4
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• pp.687-699
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• 2014

Based on the energy method considering the second order effects, the natural frequencies of externally prestressed simply supported beam and the compression softening effect of external prestress force were analyzed. It is concluded that the compression softening effect depends on the loss of external tendon eccentricity. As the number of deviators increases from zero to a large number, the compression softening effect of external prestress force decreases from the effect of axial compression to almost zero, which is consistent with the conclusion mathematically rigorously proven. The frequencies calculated by the energy method conform well to the frequencies by FEM which can simulate the frictionless slide between the external tendon and deviator, the accuracy of the energy method is validated. The calculation results show that the compression softening effect of external prestress force is negligible for the beam with 2 or more deviators due to slight loss of external tendon eccentricity. As the eccentricity and area of tendon increase, the first natural frequency of the simply supported beams noticeably increases, however the effect of the external tendon on other frequencies is negligible.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.545-552
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• 2008

To insure the quality and safety of ground anchors, pull-out test of anchor has to be done. In the individually controlled pull-out test system, pull-out device is used to introduce the same pull-out force to individual tendon that has a different length and a deflection. That is, that device has a separate pull-out oil jack to each tendon, thus the pull-out length of each jack is not the same, but that device introduces each tendon to the same pull-out force. In this study, the in-situ pull-out tests for the compression anchors were performed and its test results were analysed and compared to the results of center hole pull-out tests. In the case of pulling out each tendon using the individually controlled pull-out test device, the pull-out forces were distributed to a individual tendon. That device is excellent one that can solve the cause of unequal pull-out forces of each tendon appearing in the manufacture process and construction of anchors, and unequal pull-out forces due to the deferent length.

• Smart Structures and Systems
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• v.15 no.2
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• pp.375-393
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• 2015

In this study, local dynamic characteristics of mountable PZT interfaces are numerically analyzed to verify their feasibility on impedance monitoring of the prestress-loss in tendon anchorage subsystems. Firstly, a prestressed tendon-anchorage system with mountable PZT interfaces is described. Two types of mountable interfaces which are different in geometric and boundary conditions are designed for impedance monitoring in the tendon-anchorage subsystems. Secondly, laboratory experiments are performed to evaluate the impedance monitoring via the two mountable PZT interfaces placed on the tendon-anchorage under the variation of prestress forces. Impedance features such as frequency-shifts and root-mean-square-deviations are quantified for the two PZT interfaces. Finally, local dynamic characteristics of the two PZT interfaces are numerically analyzed to verify their performances on impedance monitoring at the tendon-anchorage system. For the two PZT interfaces, the relationships between structural parameters and local vibration responses are examined by modal sensitivity analyses.

• Journal of the Korea Concrete Institute
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• v.21 no.4
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• pp.513-521
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• 2009

Recently, the externally prestressed unbonded concrete structures are increasingly being built. The mechanical behavior of prestressed concrete beams with external unbonded tendon is different from that of normal bonded PSC beams in that the slip of tendons at deviators and the change of tendon eccentricity occurs as external loads are applied in external unbonded PSC beams. The purpose of the present paper is therefore to evaluate the flexural behavior by performing static flexural test according to tendon area and tendon force. From experimental results, before flexural cracking, there was no difference between external members and bonded members. However, after cracking, yielding load of reinforcement, ultimate load, and the tendon stress of external members was lower than that of bonded members. For the relationship of load-tendon stress, the increasing of tendon strain was inversely proportional to the initial tendon force. However, even if the initial tendon force was large, the tendon strain with small effective stress was smaller than that with large effective stress. The concrete compressive strain was proportional to the effective stress of external tendon. From the comparison between test results and codes, the ACI-318 could not consider the effect of tendon force or effective stress, and especially the results of ACI-318 were very small, so it was very conservative. And the AASHTO 1994 could be influenced on the tendon area, initial force and effective stress, but as it was made on the basis of internal unbonded tendon, its results were much larger than the test results. For this reason, the new correct predict equation of external tendon stress will be needed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.06a
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• pp.871-872
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• 2008

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.3A
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• pp.183-188
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• 2012

The bonded tendon was adopted to the reactor containment building of some operating nuclear power plants in Korea and the assessment of the prestress force on the bonded tendon is very important for the evaluation of the structural integrity. The prestress force of the bonded tendon at real reactor containment building, was evaluated using the SI technique and impact signal analysis technique which were developed to improve the existing indirect assessmment technique. For these techniques, the strain of the reactor containment building and the stress wave velocity of the bonded tendon were measured. Both SI technique and impact signal analysis technique give the highly reliable results comparison with the existing theoretical approach. Therefore, it is confirmed that the developed techniques are very useful for the evaluation of the prestress force on the bonded tendon.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.28 no.4
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• pp.369-374
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• 2015

In this paper, an EM sensing based prestressing force estimation method is proposed, in which it can estimate tensile force of PS tendon for PSC girder. The PSC girder has more improved performance than the general concrete girder by introducing the prestressing to the concrete. Thus the PSC girder bridge is widely constructed due to its high performance and low cost. However, the prestressing force has not been managed nevertheless it is major factor for the maintenance of the PSC girder bridge. The prestressing force was just measured during construction using jacking device and after that, it can not be managed. For this reason, this paper proposes a tensile force estimation method of PS tendon based on EM sensor. The permeability of ferroelectric material is changed according to the induced stress to the material, in which it can be measured using EM sensor. To measure the permeability of PS tendon, the EM sensor was fabricated and verified by performing the MTS test. The test was performed using 7-wire steel tendon under the 0, 40, 80, 120, 160, 200 KN of tensile force. The permeability of PS tendon was gradually decreased according to the increasement of tensile force. The regression method was used to find the relation between permeability and stress. As a result, the permeability has linear relation with the tensile force of PS tendon and the pre-stressing force can be estimated by the derived estimation equation.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.10
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• pp.1043-1052
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• 2009

In this work, a master-slave manipulator system which will be used for handling objects contaminated by radioactivity has been addressed. The links of manipulators are driven independently by individual motors installed on the base and the driving torque is transmitted through pre-tensioned tendons. Since the measurable variables are the positions and rates of master/slave motors, only a constrained specific bilateral control structure is available. In the consideration of the flexibility of the tendon and constrained control structure, we derived a necessity for tendon design to prevent uncontrollable vibration mode through a modal analysis. Based on a reduced rigid body model, a control design was suggested and tendons were selected. The feasibility of the proposed analysis and tendon design were verified along with some simulation results.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.6
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• pp.122-130
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• 2009

The analysis of human movement requires the knowledge of the Hill type muscle parameters, the muscle-tendon and moment arm length change as a function of joint angles. However, values of a subject's muscle parameters are very difficult to identify. It turns out from a sensitivity analysis that the tendon slack length and maximum muscle force are the two critical parameters among the Hill-type muscle model. Therefore, it could be claimed that the variation of the tendon slack length and maximum muscle force from the Delp's reference data will change the muscle characteristics of a subject remarkably. A numeric optimization method to search these tendon parameters specific to a subject is proposed, and the accuracy of the developed algorithm is evaluated through a numerical simulation.

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.4
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• pp.145-154
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• 2006

This paper presents a method to enhance the load carrying capacity for a two-span continuous steel-concrete composite beam strengthened with external tendons. The tendon is placed at the bottom of steel beam where the positive bending moment occurs. This results in the reduction of the negative bending moment as well as the positive bending moment. This paper describes the procedure to determine the number of tendon and the initial tendon force for the target rating factor in the rating factor equation. An example beam is given to demonstrate the proposed procedure, and it validity is confirmed.